1. Field of the Invention
This invention relates to light waveguides and, more particularly, to optical circuits.
2. Art Background
Optical waveguide systems are composed of a variety of constituent parts. These constituent parts include a source of light, optical waveguides, e.g., optical fibers, to carry the light produced, and a component to perform signal processing operations such as to switch signals among the optical waveguides of the system. The last component is typically fabricated from a pyroelectric material such as lithium niobate or lithium tantalate. Wavepaths generally are fabricated in the pyroelectric substrate by depositing a dopant such as titanium on the surface of the substrate in the pattern desired for the wavepaths. The substrate is then heated to diffuse the dopant into the substrate. This procedure forms a wavepath, i.e., a section in the pyroelectric material that guides light, usually about 1 to 5 .mu.m deep and 1 to 10 .mu.m wide. To cause signal processing, such as switching between wavepaths in the pyroelectric material, a voltage is imposed across the region of the crystal where the processing is desired through electrodes deposited for this purpose. This voltage produces local changes in the optical polarizability of the crystal, thus locally changing the refractive index and, in turn, effecting the processing, e.g., altering the path of light through the crystal.
Due to the relatively small cross-section of the waveguides, the alignment of the various components, such as the alignment of optical fibers with the wavepaths of the processing element, is not a trivial problem. Typically, this alignment is done with a lens and photodetector system. For example, a component with a light output, e.g., an optical fiber, is coarsely aligned with a wavepath in a switching element, and the lens system is positioned to direct the light exiting from the wavepath onto the photodetector. The component with electromagnetic radiation output is then adjusted to maximize the electromagnetic radiation exiting the wavepath as observed by the photodetector. After alignment, the lens system and detector must be repositioned for the next alignment procedure. Although positioning the lens/detector system is not as difficult as the actual alignment itself, it is time-consuming and significantly increases costs. Additionally, a lens system and photodetector are not easily adapted to use outside a laboratory environment. This limits assembly and repair of optical communication systems in places such as a cable vault.